Evolution of body axis extension and tissue spreading in the fly embryo

• Applicant: Dr. Steffen Lemke
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology)
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437994272

Body plan variation is a hallmark of animal diversity. During development, gastrulation sets up the animal body plan by segregating a homogenous cell mass into distinct germ layers, which then differentiate based on local genetic instructions. The mechanism of how this process evolved is not well understood, but arguably requires global coordination of distinct tissues. We propose that such coordination is provided by tissue-tissue interactions and mechanics. To address this hypothesis, we will study gastrulation diversity in the insect order Diptera (‘true’ flies), which we established as experimental system to characterize and experimentally test tissue evolution at the cellular level. We will focus on innovation and coordination in two separate processes that collectively dominate gastrulation in flies and other animals: the extension of the embryo proper along its head-to-tail axis, and the spreading of extraembryonic tissue to provide a yolk/embryo envelope. We will ask how body axis extension got faster, how envelope formation was lost, and how both changes globally affected development of the embryo inside a yolk rich egg. Our studies will yield novel insights into the evolvability of early development and explain how small molecular changes can multiply to have large-scale effects at the organismal level.

• DFG Programme: Research Grants